Analytical procedures carried out in clinical laboratories have, over the past decades, been automated to varying degrees in order, among other reasons, to increase productivity and to reduce human error.
Blood analysis, in particular, has benefited significantly from applying automation to those procedures. Today, many test procedures can be performed routinely on a given blood sample with great economy and reliability.
Typically the instrumentation dominating the field is based on the mechanization of the various procedural steps which previously have been performed manually by clinical technicians. Since these proven procedures are of the wet category, the instruments are involved in manipulating a variety of sample and reagent liquids, including mixing, incubating and taking measurements of the liquids. Beyond the operations directly involved in causing and in controlling the various chemical reactions, such instruments perform peripheral support activities, as for example washing and drying reaction vessels and fluid metering probes, maintaining reagent fluids at correct conditions to ensure reasonable stability, monitoring the chemical processes to eliminate errors, and analyzing and collating the resulting test data.
While the chemical procedures performed in such instruments often are relatively well established, the instruments frequently become complex as their throughput and their library of tests increase. A typical test protocol with various options includes the steps of introducing an aliquot of the sample liquid, adding reagent(s), mixing, if needed adding further reagent(s), incubating, and measuring reaction product(s). The measurement typically is a form of photometry such as colorimetry, fluorometry, nephelometry, or flame photometry; although other measurements such as spectroscopy can be used. A diversity of analytical hardware is commercially available, with each type specifically designed to meet the needs of a particular segment of the clinical laboratory community. This community can be divided into a number of distinct groups each having diverse needs. Large commercial clinical labs and clinical labs in large hospitals are the typical users of large analyzers capable of carrying out fifteen to thirty simultaneous tests on a single patient at rates of sixty to one hundred and twenty patients per hour. Such instruments usually incorporate a number of parallel test-dedicated channels, each capable of the operations recited above. Thus a ten-test instrument in this large instrument category would consist of such elements as a sample-introducing and distributing mechanism feeding each of ten separate reaction channels, and a reagent supply and delivery mechanism selectively feeding the ten channels. An analytical unit, typically with a separate measuring device for each channel, examines reaction product from each channel. Finally, a data collection and processing unit prepares an output report of the results determined in each channel for each sample fed to the system. Such instruments are costly and require a specialized support team. This makes such instruments economically justifiable only in an environment where the work load matches the relatively large capacity.
A variety of smaller instruments is available to smaller laboratories, and each is specific in its capability and features. Also, many suffer from operational deficiencies. In particular, single or dual channel bench-top analyzers are test-dedicated, relatively inexpensive instruments that can perform one or two tests at a moderate throughput. Typical tests are glucose and blood urea nitrogen, since they are popular and have clinical significance in combination. Samples are introduced manually, and an operator must transcribe displayed results.
Enzyme analyses are increasingly common in clinical laboratories, and this gives rise to different instruments each capable of performing one different class of tests. The requirement of enzyme-testing instruments is that reaction rates are measured during a time span, while the test fuid is maintained at 37.degree. C. To measure the rate of reaction, the instruments either observe the reaction continuously, or look at the reaction progress at time intervals. In general, enzyme instruments rely on extensive manual activities to introduce sample and reagents. In some instruments reagent packs are loaded into the instrument and reagent is delivered from them to the reaction vessel by pushing an appropriate reagent-selecting button. Other instruments have a single reagent capability and require reagent changeover between tests. These instruments generally perform one test at a time. Due to the fact that the observation of reaction rate requires considerable time, the throughput is relatively low, e.g. thirty to fifty tests per hour.
Emergency conditions often require that a patient be tested quickly to determine the course of treatment. This requires instrumentation which can be maintained in a standby mode, where it is ready to perform a variety of tests in a relatively short time. To fill this need, stat analyzers are provded. These instruments commonly rely on the introduction of prepackaged reagent capsules which are sequentially ordered with patient samples, in a single channel instrument, to perform the prescribed tests. Here, many of the reagent delivery processes, which are performed automatically within the large automated instruments, are done outside the analyzer. In many instances, as in the du Pont ACA apparatus, the reagent-containing packages also serve as reaction vessels and as photomertic cuvettes. Thus other chemistry-specific hardware requirements, beyond just reagents, are supplied in disposable form to the instrument.
Another class of analytical hardware, developed at Oak Ridge and commercially produced by Union Carbide, Electro-Nuclenoics and American Instrument Corp., utilizes a centrifugal disc in which previously loaded sample and reagent liquids are centrifugally mixed and moved into a cuvette compartment. Continued rotation of the disc allows a stationary detector to observe the reaction product of each of a number of patient samples as the cuvettes rotate by the detector. This type of instrument is commonly classified as a form of batch processing device, since a single test is performed on the patient samples within a single rotor. The sample fluid and reagent are loaded into the rotor disc either manually or via a fluid dispensing accessory unit off the analyzer. The analyzer thus serves as a mixing, incubation and readout/data processor device. The batch nature of the process presents a number of logistical data collating problems. Results for a patient requiring a battery of tests are not available until that number of test batches is processed. While computer oriented solutions to the logistics are available in the form of accessories, they nevertheless cannot resolve the fundamental deficiency of a long wait for a complete battery of tests.
Thus, the basic instrument unit known in the art is a single fluid-delivery/chemical-processing/readout channel. Large instruments utilize a number of such test-dedicated channels in parallel to achieve operational objectives. Smaller, single-channel instruments perform test-specific operations either manually outside the instrument or by the introduction of already-formulated test-specific disposable packages. Such solutions, while producing less costly instruments and hence affordable by smaller laboratories, require a heavier human involvement in the operation of the instrument or a higher per test cost as a result of prepackaged reagents and/or disposables, compounded by the fact that the laboratory is generally limited to a single source for such materials.